This invention relates generally to waveguides used in vehicle illumination and, in particular, to branching optical junctions used in vehicle interior illumination.
Traditionally, interior vehicle lighting has been accomplished by utilizing individual incandescent bulbs or other such light sources which are each dedicated to a single lighting function. The bulbs are placed at various locations throughout the vehicle where the illumination is needed and are energized by electrical power delivered via individual wires. As a result of the growing number of lighting applications within the vehicle, as well as the concomitant weight, cost, and power required by traditional lighting topologies, distributed lighting systems are becoming increasingly viable for use within the vehicle. These distributed lighting systems are typically implemented as light conducting networks that use fiber optics or other waveguides to deliver light from a relatively small number of light sources to remote areas of the vehicle. Generally, these remote areas are illuminated by light which is emitted from the distal end of each waveguide in conjunction with some type of lensing device, which aids in focusing, dispersing, or otherwise affecting the emitted light pattern. Many light conducting networks have been proposed over the years that cover a wide spectrum of characteristics and features.
For example, U.S. Pat. No. 5,452,186, issued Sep. 19, 1995 to Dassanayake, discloses a light distribution system which utilizes a single light source and a multitude of waveguides to illuminate various components throughout a vehicle, such as an instrument panel, interior dome light, vanity mirror and sun visor. The light source is optically coupled to a ring of waveguides, which are generally oriented perpendicular to the light source in order to receive the incident light. The incident light is then delivered through the waveguides to remote locations, where it radiates out of the waveguides for illumination of an adjacent article or region of the vehicle interior.
Another apparatus for conducting light throughout a vehicle is disclosed in U.S. Pat. No. 5,465,194, issued Nov. 7, 1995 to Currie. The Currie patent discloses various embodiments for the delivery and illumination of light throughout a vehicle, and in one embodiment discloses a light conducting Y-branch. This Y-branch includes two input waveguides which are optically coupled to a single output waveguide at a junction. This junction is fitted with a plano-convex lens which focuses the incident light from both input waveguides and therefore transmits all of the entering light to the single waveguide without any radiation out of the junction. The Y-branch arrangement disclosed by Currie enables light of different wavelengths to be transmitted through the input waveguides and mixed at the junction to thereby control the color of light outputted by the single waveguide. This patent is typical of prior art Y-branch arrangements in that it is not designed to provide illuminating light from the junction; thus, any light exiting the junction is lost and wasted.
In areas other than vehicle lighting, light distribution for purposes of illumination has also been proposed using a network of waveguides. See, for example, U.S. Pat. No. 4,721,350, issued Jan. 26, 1988 to Mori, which discloses a light distribution network that can gather light from a single source and deliver it throughout an entire office building. In one particular embodiment, Mori discloses a branching optical junction which can act as a photo-radiator to thereby illuminate the surrounding area. This embodiment includes a main light conducting channel with a transverse bore extending through it and a secondary light conducting channel that fits within the transverse bore. The distal end of the secondary channel is a mirrored, angled end which extends into the bore and thereby obstructs the light traveling within the main channel. As the light travels along the main channel, it impinges the angled end which acts as a reflection surface, diverting at least a portion of the light out of the main channel. Typically, the diverted light is distributed to the secondary channel, which then delivers the light to a remote area. However, the angled end can be used as a reflecting element for illuminating the immediately surrounding area. Instead of diverting light into a secondary channel, the mirrored surface of the angled end is used to reflect the light out the other end of the bore, which is open. In this sense, light traveling along the main channel impinges this angled surface, and thereby reflects the incident light out of the open end of the bore and illuminates the surrounding area. The angled end can be positioned at various depths within the transverse bore, and can assume different angles, both of which affect the amount of light which is diverted.
The optical junction in the Mori patent utilizes two separate waveguides which are not permanently affixed to each other. While this allows the position of the secondary, or branching, waveguide to be adjusted to different depths within the transverse bore, such a construction is believed to be overly complex for an automotive interior lighting system and therefore unnecessarily expensive and difficult to implement.
Thus, there exists a need for a branching waveguide for automotive lighting systems and other such light distribution systems that makes use of the light exiting the waveguide at the branching junction.
In accordance with the present invention there is provided an illuminated interior article system for use as a part of a vehicle interior lighting system. It includes a branching optical waveguide and a vehicle interior article positioned relative to waveguide such that the illuminating light exiting the waveguide at its junction illuminates the vehicle interior article, whether by direct, indirect, or backlit illumination. The branching waveguide has a stem, first and second branches, and a junction that couples the stem to each of the branches. The stem and branches each comprise an elongated section of the waveguide formed from an optically-transmissive material that is capable of conducting light along its length by internal reflection of the light. The first and second branches extend away from the junction at an obtuse angle relative to the stem and the junction includes one or more optical features positioned at the junction such that a portion of the light traveling through one or more of the waveguide sections impinges upon the optical feature(s), with the optical feature(s) redirecting the impinging light out of the waveguide at the junction to thereby provide illuminating light from the junction. Rather than attempting to minimize light leakage at the waveguide junction, as is done in other branching waveguide light distribution systems, the waveguide of the present invention allows light to be selectively leaked from the junction for purposes of illumination.
The optical features used to radiate light out of the waveguide at the junction can be any of a wide variety of physical features which promote light leakage including notches, stipplings, optical coatings, or outer surface configurations of the waveguide that are oriented at an angle relative to the direction of the impinging light such that the light is directed out of the waveguide rather than being internally reflected.